The present invention concerns an automatic immunoassay system, in which the inner face of the reaction vessel is used as the solid phase. The method of the invention may be used generally for photometric, fluorometric, phosphorimetric, or radiological immunoassays.
In order to determine an antibody (or antigen) present in a sample, so-called heterogeneous immunoassay methods are used, wherein the antibody (or antigen) and an antibody (or antigen) labelled with a tracer are allowed to be immobilized on an antigen (or antibody, respectively) in advance placed on a solid face. In these methods, the solid face, on which the immunological reaction has taken place, and the reaction solution are separated from each other before the signal of the tracer is measured from the solid face, in order that the excess tracer present in the reaction solution should not cover the signal in the antibody (or antigen) immobilized on the solid phase. The signal concerned may be, for example, radioactivity (RIA), fluorescence activity (FIA), or enzyme activity (EIA). In all of these methods, the solid phase must be washed carefully before the measurement.
The methods in use at present always include steps that must be performed manually; at least the washing step, for whose automation no means have been found that operate reliably in practice.
In automatized methods, attempts must be made to use sets of reaction and measurement cuvettes consisting of several sample vessels. As a rule, the reactions must be carried out at a precisely determined temperature. For the control of the temperature, incubators have been used, which comprise a heatable piece and therein a cuvette-shaped recess of its own for each cuvette in the cuvette set. This solution is, however, not satisfactory, for in this way it is difficult to make the temperatures in the different cuvettes to remain sufficiently precise at the desired level. For this reason, although the use of large cuvette sets may be desirable in these automated methods, these methods are limited to using smaller cuvette sets.